12 THE NATURE STUDY REVIEW [6:1- J an.. 1910 



food by the silo. Root crops, like potatoes, which may have 

 chanced to freeze, or have been infected by disease and would 

 otherwise spoil, may be preserved in a silo and made into good 

 food for cattle. 



When corn is allowed to ripen on the stalk there is little of 

 value for food in it beside the kernels. Cows will eat the dried 

 leaves, to be sure, if they are hungry, but the hard dry stalks 

 are not only poor food, they are a nuisance either as litter in 

 the barn yard or as obstruction to tillage of the fields. Yet 

 the stalks which grow on a single acre may, if preserved in a 

 silo while they are green, make food enough to keep half a 

 dozen cows a whole year. 



The silo which I have in mind is a wooden cylinder, 18 

 feet in diameter and 30 feet high. It cost $175 and will hold 

 150 tons of green corn stalks. It furnishes three quarters of 

 the coarse feed given to 30 cows during eight months of each 

 year. 



We let the corn grow until the lower leaves begin to turn 

 yellow and the kernels begin to dent. We then cut it while 

 the stalks are still juicy and the kernels are still full of milk. 

 We chop this — stalks, leaves, kernels, cobs, and all — into very 

 small pieces and pack the silo with it as tight as possible. In 

 two or three days this mass begins to ferment and grow hot — 

 about as hot as a hot bath, say no degrees F. We call it silage. 



An interesting experiment may be performed, to parallel 

 this process in a small way, by chopping some green stuff and 

 packing it in a large pail, or ash can, with a cover. Thrust a 

 long-stemmed thermometer down into this mass to note its 

 temperature from day to day. 



We are familiar with the fact that animals are warm while 

 they live but grow cold when they die. We connect this with 

 the fact that they take in oxygen from the air, cause it to 

 unite with carbon in their bodies and give out carbon dioxide. 

 We show the presence of this carbon dioxide gas in the breath 

 by breathing into a wide mouthed bottle containing a spoonful 

 of lime water, shaking it and noting that it becomes milk white. 

 Plants likewise absorb oxygen from the air and give out car- 

 bon dioxide. This process in plants likewise produces heat — 

 although slowly, because the process is slow in them. Hence 

 we do not think of plant heat as we do of animal heat; ordinarily 

 the heat escapes as fast as it is produced and does not ac- 

 cumulate sufficiently for us to detect it. 



